A common issue for the Raspberry Pi is an inadequate power supply. 
Noralf Trønnes started a discussion [1] about writting such under-voltage
conditions into the kernel log.

This series is a draft to upstream the resulting kernel patch and is not
intended for 4.18.

[1] - https://github.com/raspberrypi/linux/issues/2367

Stefan Wahren (6):
  ARM: bcm2835: Add GET_THROTTLED firmware property
  dt-bindings: hwmon: Add Raspberry Pi voltage sensor
  hwmon: Add support for RPi voltage sensor
  ARM: bcm2835_defconfig: Enable RPi voltage sensor
  ARM: multi_v7_defconfig: Enable RPi voltage sensor
  arm64: defconfig: Enable RPi voltage sensor

 .../bindings/hwmon/raspberrypi-hwmon.txt           |  19 ++
 arch/arm/configs/bcm2835_defconfig                 |   2 +-
 arch/arm/configs/multi_v7_defconfig                |   1 +
 arch/arm64/configs/defconfig                       |   1 +
 drivers/hwmon/Kconfig                              |  10 +
 drivers/hwmon/Makefile                             |   1 +
 drivers/hwmon/raspberrypi-hwmon.c                  | 207 +++++++++++++++++++++
 include/soc/bcm2835/raspberrypi-firmware.h         |   1 +
 8 files changed, 241 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/devicetree/bindings/hwmon/raspberrypi-hwmon.txt
 create mode 100644 drivers/hwmon/raspberrypi-hwmon.c

-- 
2.7.4


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